1. Field of the Invention
The present invention relates to a switch, and more particularly to an overload protection switch in which a conductor is provided to connect the first primary leg to the second primary leg so that not only will the current passing along the primary leg cause temperature rise in the bi-metal plate, but also the heat generated in the conductor will cause the temperature of the bi-metal plate to rise so that overload to the switch is avoided.
2. Description of Related Art
Overload protection devices provided for safety when using electrical appliances are commonly used in our daily lives. FIGS. 5 and 6 show a conventional overload protection switch. The switch has a hollow housing (50) and a button (60).
The button (60) has two bosses (600) respectively formed on two opposite sides of the button (60) to correspond to two pivot holes (500) respectively defined in opposite sides of an upper portion of the housing (50), a first leg (61) extending downward from a bottom side of the button (60) and a second leg (62) also extending downward from the bottom side of the button (60).
The housing (50) has a primary connection leg (51) securely mounted on an inner side and partially extending out of the hollow housing (50). The primary connection leg (51) is provided with a first contact (510) securely mounted on a top portion of the primary connection leg (51). A second connection leg (52) is extended out of the housing (50). A bi-metal plate (53) has a first distal end securely connected to the second connection leg (52) and a second distal end provided with a second contact (530) to correspond to the first contact (510) of the primary connection leg (51). A deformation (531) is formed in a mediate portion of the bi-metal plate (53).
When the switch is to be assembled, the two bosses (600) are respectively extended into the pivot holes (500) to allow the button (60) to pivot relative to the housing (50). After the primary leg (51) and the second connection leg (52) are securely received in the housing (50), two supports (54,55) are also securely received in the housing (50) to sandwich the dual metal plate (53). Thus, when the switch is in use, the button (60) is first pivoted to cause the second contact (530) to engage with the first contact (510) of the primary leg (51) to have the switch to be in “ON” status. When the button (60) is pivoted again, the second contact (530) is forced by the second leg (62) to leave the engagement with the first contact (510) to have the switch to be in “OFF” status, as shown in FIG. 7.
When the switch is on and if the current passing through the switch is excessive, the temperature of the bi-metal plate (53) will rise and the deformation (531) will expand to cause the separation between the first contact (510) and the second contact (530) as a consequence. Therefore, whenever there is an overload in the switch, the movement of the bi-metal plate (53) will automatically shut off the connection between the first contact (510) and the second contact (530) so that the electrical appliance electrically connected to the switch is protected from damage.
However, if the designated ampage to pass through the bi-metal plate is 3 A and the electrical appliance connected to the switch has an ampage tolerance lower than 3 A, the movement of the bi-metal plate will not protect the appliance from overloading.
To overcome the shortcomings, the present invention tends to provide an improved overload protection switch to mitigate the aforementioned problems.